6.子路由

{
    path:'news',
    component:NewsComponent,
    children:[
      {
        path:"morning",
        component:MorningComponent
      },{
        path:"night",
        component:NightComponent
      },{
        path:"",
        redirectTo:"morning",
        pathMatch:"full"
      }
    ]
  }

//在父路由对应的组件中的html中
<router-outlet></router-outlet>